Innovative Intersections and Interchanges
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What Is An Echelon?
- A grade-separated intersection where one approach on both roadways is elevated to create a pair of
- Both intersections are signalized and operate like conventional one-way street intersections
- There are no free-flow movements
- Uses retaining walls to elevate half of the roadway while the other half continues at-grade
- All pedestrian sidewalks and crosswalks are at grade. However, a staircase or ramp may be required in some locations due to retaining walls or other obstacles
When Should It Be Considered?
- With heavy traffic where main and side street traffic volumes are similar
- Where an at-grade conventional intersection is not sufficient for the traffic
- Where there is limited right of way to expand
- Improved safety: Reduces the number of points where vehicles cross paths and decreases the potential for angle crashes
- Increased efficiency: Each intersection operates with only two traffic signal phases, allowing the intersection to handle more traffic
- Shorter wait times: Fewer traffic signal phases means less time stopped at the intersection
- Cost savings: The echelon can have a narrower cross section and may be more cost effective than constructing a traditional diamond interchange
How to Navigate
The number of conflict points (locations where vehicle travel paths intersect) is one metric that can be used to evaluate the safety of an innovative intersection or interchange.
There are three categories: crossing, merging or diverging.
In general, merging and diverging conflict points — where vehicles are moving in the same direction — are associated with less severe crash types than crossing conflict points where vehicles are moving in opposite directions.
The diagrams below compare possible vehicle travel movements and associated conflict points at a conventional four-leg intersection to an echelon.
These diagrams represent a general case, with one travel lane in each direction, and do not take into account pedestrian or bicycle movements at an intersection or interchange.
When compared to a conventional four-leg intersection, an echelon has 10 fewer crossing conflict points.
Conventional Intersection: Conflict Points
Echelon: Conflict Points